This invention relates to heat transfer metallization and more particularly, to heat transfer decorations with patterned metallization.
Patterned metallization can be achieved by removing portions selectively of a metallized web. One procedure is to use sodium hydroxide caustic to selectively remove vacuum-deposited aluminum.
Thus, in U.S. Pat. No. 4,685,997 a patterned laminate is formed by printing an etchant image on a metallized web. The etchant dissolves the metallized surface in the printed areas to provide the desired pattern. Variants of the procedure are found in U.S. Pat. No. 4,610,755 and 4,552,614. In 4,610,755 a water-based varnish with a dissolved etchant is printed on a metallized surface. In 4,552,614 an aqueous etchant is sprayed on the metallized surface.
Another variant is disclosed in U.S. Pat. No. 4,517,045, U.S. Pat. No. 4,398,994 and Canadian 1,141,273. A pattern is formed on an aluminized polymer film by printing with sodium hydroxideresistant material. The non-overprinted areas are then contacted with hot aqueous sodium hydroxide solution to dissolve the nonprinted aluminum, which is washed from the film.
The foregoing procedures cannot be used with conventional heat transfer material because the results are unsatisfactory. The metal patterns tend to become dull and molted in transfer.
In a hot stamp foil that transfers bright metal as a decoration there is typical employment of this brittle protective lacquer. These lacquers are used as in U.S. Pat. No. 4,275,116 to immobilize the metal layer. Dimensional and thermal stability of 1.5 to 4 percent elongation layer are imparted by polymester film. Application of thick backing layers other color or adhesives impart mobility and destroy metal film layer integrity.
In general there is a demand for heat transfer decorations with bright metal graphics. This cannot be achieved with the protective lacquers used for thermally transferring conventional graphics to compound curves. Lacquers which soften below 350.degree. F. (175.degree. C.) stretch upon heat transfer above 200.degree. F. (100.degree. C.) and vacuum-deposited bright metal layers turn dull. Metal layers which were restricted from breaking up by the proximity to the polyester film in standard hot-stamped foils would turn matte upon transfer to a compound curve with additional graphics and metal protection.
On the other hand, one would not expect that coatings with softening points above 350.degree. F. (175.degree. C.) and elongations ranging from 6 to 80 percent at thicknesses up to 25 microns could stabilize this type of multi layer construction by keeping the metal from shifting and turning dull.
Accordingly, it is an object of the invention to permit high speed heat transfer of multi-colored graphics with protected specular metal to compound curves from a carrier web.